Method and Apparatus for Transmitting Sidelink Feedback in a Wireless Communication System

Abstract

In an example, a first User Equipment (UE) receives a sidelink transmission, associated with enabled sidelink Hybrid Automatic Repeat Request (HARQ) feedback, from a second UE in a first timing. The first UE attempts to access a channel for transmission of a sidelink HARQ feedback in a first feedback resource in a second timing. The sidelink HARQ feedback is in response to the sidelink transmission. The attempt to access the channel for the transmission of the sidelink HARQ feedback in the first feedback resource fails. The first UE performs channel access for a second feedback resource. The second feedback resource is within a window and/or within a predefined duration of the first timing or the second timing. In response to successfully performing the channel access, the first UE performs, in the second feedback resource, a sidelink feedback transmission of the sidelink HARQ feedback to the second UE.

1 . A method of a first User Equipment (UE) performing sidelink communication in a sidelink resource pool, the method comprising:
 receiving a sidelink transmission from a second UE, wherein the sidelink transmission is associated with enabled sidelink Hybrid Automatic Repeat Request (HARQ) feedback;   attempting to access a channel for transmission of a sidelink HARQ feedback in a first feedback resource, wherein:
 the sidelink HARQ feedback is in response to the sidelink transmission; and 
 attempting to access the channel for the transmission of the sidelink HARQ feedback in the first feedback resource fails; 
   performing channel access for a second feedback resource, wherein:
 the second feedback resource is within a window; and 
 the channel access for the second feedback resource is performed successfully; and 
   in response to successfully performing the channel access for the second feedback resource, performing, in the second feedback resource, a sidelink feedback transmission of the sidelink HARQ feedback to the second UE.   
     
     
         2 . The method of  claim 1 , wherein at least one of:
 the first UE receives the sidelink transmission in a first timing;   the first feedback resource is in a second timing;   the first UE performs the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource in a third timing;   the first timing is before the second timing; or   the second timing is before the third timing.   
     
     
         3 . The method of  claim 2 , wherein at least one of:
 the method comprises determining a beginning of the window based upon the first timing or the second timing;   a duration of the window corresponds to a predefined value;   the window is associated with retransmission, of the sidelink HARQ feedback, without reception of a signal from the second UE;   the window is associated with retransmission, of the sidelink HARQ feedback, without triggering resource selection;   the window is different than channel occupancy time; or   the first UE performs the sidelink feedback transmission of the sidelink HARQ feedback during the window.   
     
     
         4 . The method of  claim 3 , comprising:
 determining whether or not to trigger resource selection for the sidelink feedback transmission of the sidelink HARQ feedback based upon whether or not the third timing is during the window, wherein the first UE performs the sidelink feedback transmission of the sidelink HARQ feedback without triggering resource selection based upon a determination that the third timing is during the window.   
     
     
         5 . The method of  claim 1 , wherein at least one of:
 the sidelink feedback transmission of the sidelink HARQ feedback is performed using a Physical Sidelink Feedback Channel (PSFCH) format associated with delivery of multiple sidelink HARQ feedbacks; or   the sidelink feedback transmission of the sidelink HARQ feedback is a PSFCH transmission.   
     
     
         6 . The method of  claim 1 , wherein:
 the sidelink transmission is scheduled by a Sidelink Control Information (SCI); and   the SCI provides a HARQ process number, of the second UE, for the sidelink transmission.   
     
     
         7 . The method of  claim 1 , wherein at least one of:
 a first parameter in the sidelink resource pool indicates whether or not retransmission of the sidelink HARQ feedback is supported;   a second parameter associated with PC5 Radio Resource Control (RRC) signaling between the first UE and the second UE indicates whether or not retransmission of the sidelink HARQ feedback is supported; or   the method comprises determining, based upon at least one of the first parameter or the second parameter, whether or not to at least one of:
 retransmit the sidelink HARQ feedback; or 
 perform the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource. 
   
     
     
         8 . The method of  claim 7 , comprising:
 determining a Channel Busy Ratio (CBR), wherein at least one of:
 the CBR is used to at least one of disable or enable retransmission of the sidelink HARQ feedback; 
 the method comprises determining, based upon a comparison of the CBR is with a threshold, whether or not to perform the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource; or 
 the first UE performs the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource based upon a determination that the CBR is not larger than the threshold. 
   
     
     
         9 . The method of  claim 1 , wherein:
 the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource corresponds to a retransmission of the sidelink HARQ feedback.   
     
     
         10 . The method of  claim 1 , wherein at least one of:
 a first parameter in the sidelink resource pool indicates whether or not the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource is supported; or   a second parameter associated with PC5 Radio Resource Control (RRC) signaling between the first UE and the second UE indicates whether or not the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource is supported.   
     
     
         11 . The method of  claim 10 , comprising:
 determining a Channel Busy Ratio (CBR), wherein at least one of:
 the CBR is used to at least one of disable or enable the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource; 
 the method comprises determining, based upon a comparison of the CBR is with a threshold, whether or not to perform the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource; or 
 the first UE performs the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource based upon a determination that the CBR is not larger than the threshold. 
   
     
     
         12 . The method of  claim 1 , wherein at least one of:
 the first UE performs the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource in response to failing to access the channel for the transmission of the sidelink HARQ feedback in the first feedback resource; or   the first UE performs the channel access for the second feedback resource in response to failing to access the channel for the transmission of the sidelink HARQ feedback in the first feedback resource.   
     
     
         13 . A method of a first User Equipment (UE) performing sidelink communication in a sidelink resource pool, the method comprising:
 receiving a sidelink transmission from a second UE in a first timing, wherein the sidelink transmission is associated with enabled sidelink Hybrid Automatic Repeat Request (HARQ) feedback;   attempting to access a channel for transmission of a sidelink HARQ feedback in a first feedback resource, wherein:
 the sidelink HARQ feedback is in response to the sidelink transmission; 
 attempting to access the channel for the transmission of the sidelink HARQ feedback in the first feedback resource fails; and 
 the first feedback resource is in a second timing; 
   performing channel access for a second feedback resource, wherein:
 the second feedback resource is within a predefined duration of the first timing or the second timing; and 
 the channel access for the second feedback resource is performed successfully; and 
   in response to successfully performing the channel access for the second feedback resource, performing, in the second feedback resource, a sidelink feedback transmission of the sidelink HARQ feedback to the second UE.   
     
     
         14 . The method of  claim 13 , wherein at least one of:
 the first UE performs the sidelink feedback transmission of the sidelink HARQ feedback in a third timing;   the first timing is before the second timing; or   the second timing is before the third timing.   
     
     
         15 . The method of  claim 13 , wherein at least one of:
 the predefined duration is associated with retransmission, of the sidelink HARQ feedback, without triggering resource selection; or   the method comprises determining whether or not to trigger resource selection for the sidelink feedback transmission of the sidelink HARQ feedback based upon whether or not the sidelink feedback transmission is within the predefined duration of the first timing or the second timing, wherein the first UE performs the sidelink feedback transmission of the sidelink HARQ feedback without triggering resource selection based upon a determination that the sidelink feedback transmission is within the predefined duration of the first timing or the second timing.   
     
     
         16 . The method of  claim 13 , wherein at least one of:
 the sidelink feedback transmission of the sidelink HARQ feedback is performed using a Physical Sidelink Feedback Channel (PSFCH) format associated with delivery of multiple sidelink HARQ feedbacks; or   the sidelink feedback transmission of the sidelink HARQ feedback is a PSFCH transmission.   
     
     
         17 . The method of  claim 13 , wherein at least one of:
 a first parameter in the sidelink resource pool indicates whether or not retransmission of the sidelink HARQ feedback is supported;   a second parameter associated with PC5 Radio Resource Control (RRC) signaling between the first UE and the second UE indicates whether or not retransmission of the sidelink HARQ feedback is supported;   a third parameter in the sidelink resource pool indicates whether or not the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource is supported;   a fourth parameter associated with the PC5 RRC signaling between the first UE and the second UE indicates whether or not the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource is supported; or   the method comprises determining, based upon at least one of the first parameter, the second parameter, the third parameter or the fourth parameter, whether or not to at least one of:
 retransmit the sidelink HARQ feedback; or 
 perform the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource. 
   
     
     
         18 . The method of  claim 13 , comprising:
 determining a Channel Busy Ratio (CBR), wherein at least one of:
 the CBR is used to at least one of disable or enable at least one of retransmission of the sidelink HARQ feedback or the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource; 
 the method comprises determining, based upon a comparison of the CBR is with a threshold, whether or not to perform the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource; or 
 the first UE performs the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource based upon a determination that the CBR is not larger than the threshold. 
   
     
     
         19 . The method of  claim 13 , wherein:
 the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource corresponds to a retransmission of the sidelink HARQ feedback.   
     
     
         20 . The method of  claim 13 , wherein at least one of:
 the first UE performs the sidelink feedback transmission of the sidelink HARQ feedback in the second feedback resource in response to failing to access the channel for the transmission of the sidelink HARQ feedback in the first feedback resource; or   the first UE performs the channel access for the second feedback resource in response to failing to access the channel for the transmission of the sidelink HARQ feedback in the first feedback resource.